EP1513168A2 - Method and apparatus for magnetising a magnet system - Google Patents

Abstract

The method involves providing the magnet system with a magnetizing coil (22) and applying a current pulse to the coil of limited pulse duration to create a magnetic field that interacts with the magnet system. The pulse duration of the current pulse is limited to a value between 10 microseconds and 500 microseconds, preferably between 10 and 200 microseconds. Independent claims are included for the use of the method to magnetize permanent magnets made of rare-earth materials; and for an apparatus for magnetizing a magnet system.

Description

The present invention relates to a method and a Device for magnetizing a magnet system according to Preambles of the independent claims. The invention is suitable for. For example, permanent magnets made of rare earth materials on the rotor of an electric motor too magnetizing and magnetically anchoring. She can in automated magnetizing systems with low cycle times or high quantities are used.

It is known for magnetizing permanent magnets Magnetizing coil to use. The magnetizing coil is immediately above the magnetic body to be magnetized or arranged around him. The magnetizing coil is a associated with charged capacitor, which via the coil unloaded. That in the magnetizing coil at short notice built-up magnetic field magnetizes the magnetic body. To one to build up enough large magnetic field, one must Magnetizing coil with many turns or a large Inductance can be used. The usual pulse durations be 10 ms or more. It is observed that the magnetizing coil undesirably strongly heated, which a high clock frequency makes it impossible and the use of complex cooling systems conditional.

One for the operation of generic Magnetizing devices suitable electrical Pulse generator is disclosed in DE-28'06'000. This Pulse generator includes a circuit for Energy recovery with two capacitors or two simultaneously fired high-current switches.

Permanent magnets made of rare earth materials such as neodymium-iron-boron (NdFeB) currently solve the large numbers used ferrite from. They are because of their high Coercive force considerably more difficult to magnetize. While dating for the magnetization of conventional magnets Magnetic alloys or ferrites a magnetic field strength of 800 kA / m is enough, modern magnets demand 1600-4000 kA / m. The latter field strength is higher than the degree of saturation of all known ferromagnetic Materials. An iron yoke for the magnetizing coil therefore has at most a supporting effect, can but cause no more field concentration. For the Magnetizing must therefore be used air coils. These have a much lower efficiency in the Magnetization, because the magnetic field is not on the Let magnets concentrate. That's why essential higher powers are brought into the coil, and whose unwanted heating is correspondingly greater.

Conventional magnetizing systems work with pulse durations of 10 ms or more. Such pulse durations give sufficient Penetration depths of the magnetic field also in electrical conductive materials, where the spread of magnetic Fields is delayed by eddy currents. They allow further the use of cost-effective electrolytic capacitors for Energy storage for the magnetizing pulse and the application of semiconductor switches for the mains frequency. For individual Magnetization in laboratory and manufacturing area is suitable This technique is good, but not for mass production. In Series production lacks the time to cool down Magnetizing coil between the individual Magnetisiervorgängen. For modern permanent magnets with high coercive force is the Performance of such a Magnetisieranlage in the Serial production limited.

In a confined space for the magnetizing coil can be Magnets in the assembled state with conventional methods hardly magnetize. In this case, beforehand magnetized permanent magnets built into the magnet system, which special demands on the assembly. The handling of magnetized permanent magnets and magnet systems delicate because ferromagnetic particles of any kind attracted and can hardly be removed. The same applies to Chipping the magnets, as they are at a accidental impact of the permanent magnets inevitably result.

Without Magnetisierpulse comes in DE-100'49'766 disclosed arrangement for magnetizing magnet systems out. According to this document, one of a coolable High-temperature superconductor constructed magnetizing coil used, which by a controllable DC source is fed. This arrangement requires a complex Cooling and consuming a lot of energy. The magnetizing coil off a high temperature superconductor is expensive and trouble-prone.

In DE-39'34'691 a device is described, in which the magnets in a current-carrying conductor be pushed. A magnetizing of pre-assembled Magnets can not be reached with this device. The in DE-39'34'691 mentioned parallelization refers on adjacent conductors for magnetizing long bar magnet or multi-pole Magnetization.

It is an object of the invention, a method and a To provide a device for magnetizing permanent magnets, which do not have the above-mentioned disadvantages. The The method and the device should be particularly also allow permanent magnets made of rare earth materials in Series production with a high clock rate of one second or less magnetizing and so high productivity too guarantee. The method and the device are intended for the use in an automated production plant be suitable, while also magnetizing already to allow magnets wound on rotors. she should work energy-saving and get along with air cooling. Furthermore, the device should be compact, robust and be cost-effective and if possible standard components use.

These and other objects are achieved by the method and the Device solved, as in the independent Claims are defined. advantageous Embodiments are in the dependent claims specified.

According to the invention, the material to be magnetized with a current flowing through a Magnetisierspule current pulse or the magnetic field built up by the magnetizing coil magnetized and magnetically anchored. The magnetization by the magnetic field is the heating of the magnetizing coil opposite. Therefore, the current pulse has to be short enough to avoid any to cause too much warming. According to the invention is a Current pulse with a pulse duration between 10 μs and 500 μs and preferably used between 10 μs and 200 μs. Of the Power pulse must be strong enough at the same time, however, for a the magnetization to build up sufficient magnetic field. The one required short pulse with strong magnetic field becomes preferably by superposition of several Magnetizing coils with low number of turns achieved.

Accordingly, in the inventive method for Magnetizing a magnet system to the magnet system Magnetizing assigned. The magnetizing coil is with subjected to a current pulse with a limited pulse duration, whereby a magnetic field interacting with the magnet system is built. In this case, the pulse duration of the current pulse on a value between 10 μs and 500 μs and preferably limited between 10 μs and 200 μs. In a preferred Embodiment become the magnet system at least two Magnetizing associated and thus mutually arranged that reinforcing their magnetic fields superimpose, and the magnetic fields of at least two Magnetizing coils are set up at the same time.

The inventive device for magnetizing a Magnet system includes a pulse generator circuit with a capacitor element, one with the capacitor element electrically connected magnetizing coil and a Switching element, by its actuation the magnetizing coil with a by discharge of the capacitor element resulting current pulse with limited pulse duration acted upon and thus the structure of a magnetic field is triggerable. The pulse generator circuit is such constructed that the pulse duration of the current pulse to a value between 10 μs and 500 μs and preferably between 10 μs and 200 μs is limited.

In a preferred embodiment, at least two Magnetizing available and so mutually arranged that reinforcing their magnetic fields overlay, and at least one switching element is such arranged and operable that the at least two Magnetizing simultaneously with one current pulse can be acted upon. Each of the at least two Magnetizing coils may be assigned a switching element, in which case the device further comprises actuating means has, by means of which the at least two switching elements can be actuated simultaneously.

In a particularly advantageous embodiment of the The device according to the invention is the pulse generator circuit several times, for example four to twelve times, existing, what in Following as "parallel multiplication" or Referred to as "parallelization" of the pulse generator circuit becomes. Thanks to parallel multiplication, the Inductance of the magnetizing coil and the capacity of the Capacitor element are kept small in the resonant circuit. This results in the required short pulse durations of eg 100 μs; nevertheless, enough high magnetic fields generated to modern, sophisticated magnet systems too magnetize.

For a reduction of heat energy in the Magnetizing coil is released, so is the Magnetizing pulse in its duration to limit. The usual Discharge circuit with freewheeling diode sets a substantial Proportion of the pulse energy stored in the capacitor exponentially decaying end of the pulse around. this section but no longer has a magnetizing effect. With a novel circuit, which in the path of the freewheeling diode a Storage throttle has, can be the exponential Prevent leakage of the current in the magnetizing coil and regain much of the energy in it. The inductive feedback allows the second swing the capacitor voltage and thereby prevents the ohmic Losses due to decaying. The remaining energy charges the capacitor element already for the next pulse again on. Thus, a low energy consumption is achieved, and it No elaborate cooling of the coil is necessary. The second Swinging over the inductive feedback results in a quadruple parallelization of the magnetizing coil one additional energy savings of 43%. Without parallelization, with a single magnetizing coil and the same power, it is only 18%.

Accordingly, preferably, the pulse generator circuit a return path arranged parallel to the magnetizing coil on which a storage throttle and a direction includes the current pulse blocking diode element. The Storage throttle element is advantageously so dimensioned that together with the storage capacitor forms a resonant circuit whose period is greater as the corresponding one of the magnetizing circuit.

The electromagnetic resonant circuit can by an already magnetized permanent magnet, preferably a NdFeB magnet, get supported. This one will be in the Magnetizing coil inserted in such a way that its field that of Coil superimposed and reinforcing effect.

For the magnetization of typical magnet systems are Performances necessary, the voltages of 1000 V and more as well Currents in the range of Kiloampere condition. The inventive device can be with about 1000 V operate, reducing the requirements for the paint insulation (125 V per turn with 8 turns) between individual Wire windings in the magnetizing coil still in the unproblematic area lie. As energy storage preferably pulse-resistant capacitors with metallized Plastic film used. These have a low Self-inductance, what the characteristics of the resonant circuit less influenced. For switching the voltages and currents come z. B. bipolar transistors with insulated gate or fast thyristors in question.

Fig. 1

einige wichtige Elemente der erfindungsgemässen Vorrichtung in einer sehr schematischen perspektivischen Ansicht,

Fig. 2

eine Pulsgeneratorschaltung für die erfindungsgemässe Vorrichtung,

Fig. 3

einen zeitlichen Verlauf verschiedener Grössen beim erfindungsgemässen Verfahren in einem Diagramm,

Fig. 4

ein Schaltelement für die erfindungsgemässe Vorrichtung,

Fig. 5

eine Anordnung von Magnetisierspulen des erfindungsgemässen Verfahrens in einer Draufsicht und

Fig. 6

einen Querschnitt entlang der Linie VI-VI durch die Anordnung von Fig. 5.

Hereinafter, advantageous embodiments of the invention will be explained in detail with reference to the drawings. Showing:

Fig. 1

some important elements of the device according to the invention in a very schematic perspective view,

Fig. 2

a pulse generator circuit for the device according to the invention,

Fig. 3

a time course of different sizes of the inventive method in a diagram,

Fig. 4

a switching element for the device according to the invention,

Fig. 5

an arrangement of Magnetisierspulen the inventive method in a plan view and

Fig. 6

a cross section along the line VI-VI through the arrangement of Fig. 5th

FIG. 1 shows very schematically important elements of a preferred embodiment of the device 1 according to the invention. The device 1 includes a plurality of preferably identical pulse generator circuits 2.1-2.4. In the embodiment of Figure 1, four such pulse generator circuits 2.1-2.4 are indicated; but it can also be more or less. Each pulse generator circuit 2.1-2.4 has a capacitor element 21, preferably a foil capacitor, and a magnetizing coil 22 electrically connected to the capacitor element 21. Each pulse generator circuit 2.1-2.4 also has a switching element 23, for example a thyristor, by the actuation of which a pulse-like discharge of the capacitor element 21 via the magnetizing coil 22 and thus the establishment of a magnetic field in the magnetizing coil 22 can be triggered. The device 1 further comprises actuating means 3, by means of which the switching elements 23 of the at least two pulse generator circuits 2.1-2.4 are simultaneously actuated. Such actuating means are known in the art; see, for. B. Werner Lücking, "Thyristor basic circuits: Manual for training, study and practice", VDE-Verlag, 1984. The pulse generator circuits 2.1-2.4 and in particular the Magnetisierspulen 22 are mutually arranged so that their magnetic fields superimpose reinforcing. Details of the pulse generator circuits 2.1-2.4 will be discussed further with reference to FIG.

FIG. 2 shows a preferred embodiment of a pulse generator circuit 2 for the device 1 according to the invention. The capacitor 21 having a capacitance C, magnetizing coil 22 having an inductance L and thyristor 23 and introduced already on the basis of FIG Inductance L ₂ , the magnetizing coil 22 an inner resistor R ₁ and the thyristor 23 and the electrical lines connecting these elements an internal resistance R ₂ .

The pulse generator circuit 2 is designed and dimensioned such that the discharge of the capacitor element 21 has a pulse duration of approximately 10-500 μs and preferably approximately 10-200 μs. To achieve such short pulse durations, the values of C and L must be small. It may, for example, apply: 1 μH <L <15 μH and 15 μF <C <150 μF, and preferably 2 μH <L <8 μH and 30 μF <C <75 μF. In order to build up sufficiently high magnetic fields despite the small L and C values, preferably the pulse generator circuit 2 or parts thereof are multiplied in parallel, as illustrated and explained with reference to FIG. The at least one capacitor element 21 should be chargeable with voltages μC of approximately 100-5000 V and preferably approximately 1200-2000 V. The pulse generator circuit 2 should allow discharge currents iL ₁ of approximately 1-10 kA and preferably approximately 2-5 kA.

In the particularly advantageous embodiment of FIG. 2, a return path 24 is arranged parallel to the magnetizing coil 22. This includes a storage inductor coil 25 having an inductance L _d and a blocking in the direction of the discharge current pulse diode 26. The storage inductor coil 25 has an internal resistance R _d . With the return path 24, the exponential leakage of the current in the magnetizing coil 22 can be suppressed and the energy stuck in it largely recovered. The storage choke coil 25 is advantageously dimensioned so that it forms a resonant circuit together with the capacitor element 21 whose period is greater, for example. 2 to 1000 times greater and preferably 10 to 100 times greater than the corresponding period of the Magnetisierkreises without return path 24. To achieve this, a storage choke coil 25 is preferably selected, which has an inductance L _d , which is 2 to 1000 times larger and preferably 10 to 100 times greater than the inductance L _{1 of} the magnetizing coil, z , B. 10 μH <L _d <150 μH.

Kurve 91: der Ladespannung uLade = uC - uL₂,

Kurve 92: des Magnetisierstroms iL₁,

Kurve 93: des Stroms iL₂ und

Kurve 94: der Diodenspannung uD.

Referring to Figure 3, a preferred embodiment of the inventive method is explained, which relates to the pulse generator circuit 2 of Fig. 2. The diagram of Fig. 3 shows a mathematical simulation of the time course of different quantities, namely:

Curve 91: the charging voltage uLade = uC - uL ₂ ,

Curve 92: of the magnetizing current iL ₁ ,

Curve 93: of the current iL ₂ and

Curve 94: the diode voltage uD.

The different phases of the temporal sequence are for Clarification by three vertical lines from each other demarcated.

uC(t=0) = 1000 V

C = 60 µF

L₂ = 2.66 µH

L₁ = 5.49 µH

R₁ = 0.062 Ω

R₂ = 0.01 Ω

L_d = 54.9 µH = 10L₁

R_d = 0.1 Ω.

The simulation is based on the following values:

μC (t = 0) = 1000V

C = 60 μF

L ₂ = 2.66 μH

L ₁ = 5.49 μH

R ₁ = 0.062 Ω

R ₂ = 0.01 Ω

L _d = 54.9 μH = 10L ₁

R _d = 0.1 Ω.

maximaler Spulenstrom iL_1,max = 2348 A

Pulsdauer = 71 µs

uLade(Ende) = 658 V

Energie(t=0) = 30 Ws

Energie(Ende) = 43 % der Energie(t=0).

The result is the following values:

maximum coil current iL _{1, max} = 2348 A.

Pulse duration = 71 μs

uLade (end) = 658V

Energy (t = 0) = 30 Ws

Energy (end) = 43% of energy (t = 0).

The switching element 23 of the device 1 according to the invention may, instead of the thyristor shown by way of example in FIG. 2, also comprise an insulated gate bipolar transistor 4 (insulated gate bipolar transistor, IGBT). Such a switching element 23 is shown by way of example in FIG . The collector C of the IGBT 4 is electrically connected to the magnetizing coil 22. Between the magnetizing coil and the IGBT, a diode 41 blocking the direction of the discharge current pulse may optionally be connected. The gate G of the IGBT 4 is driven by a drive device 42. The drive unit 42 has an ignition input 43 for an ignition pulse. After the emitter E of the IGBT 4, a current sensor 44 is installed, the signal of which is fed via a sensor input 45 into the drive unit 42. If the emitter current I _{E is} positive and a firing pulse is present, the IGBT 4 should let through; otherwise the IGBT 4 should lock.

FIG. 5 shows a preferred arrangement of magnetizing coils 22.1-22.8 in the device 1 according to the invention in a plan view. FIG. 6 shows a cross section along the line VI-VI in FIG. 5. In this exemplary embodiment, eight magnetizing coils 22.1 to 22.8 having different diameters are nested one inside the other. Each magnetizing coil 22.1-22.8 has, for example, six turns. It is also possible to use magnetizing coils with bifilar or multifilar windings. The magnetizing coils 22.1-22.8 may be rectangular, square or round or have other geometries. The arrangement can be completed on both sides by an epoxy glass plate 27.1, 27.2. The inner or outer diameter of such an arrangement depends on the particular application and is typically in the range of a few to a few hundred centimeters. The resulting magnetic field B, ie the superposition of the magnetic fields built up in the eight magnetizing coils 22.1-22.8, is indicated by an arrow. The arrangement is z. B. positioned on the surface of a magnetic system to be magnetized 8, such that the largest possible part of the magnetic field B can interact with the material of the magnetic system 8. If the magnet system 8 is accessible, at least partially, from the sides, the arrangement is preferably positioned such that the magnetizing coils 22.1-22.8 surround, at least partially, the magnet system 8. This allows an even more efficient magnetization to be achieved.

Alternatively to the embodiment shown here, the Magnetizing coils 22.1-22.8 also the same diameter have and be arranged one above the other. Of course, combinations of Nesting and arrangement on top of each other possible.

LIST OF REFERENCE NUMBERS

1

contraption

2

Pulse generator circuit

21

capacitor element

22

magnetizing

23

switching element

24

Return path

25

Storage inductor

26

diode

27.1, 27.2

Epoxy-glass plate

3

actuating means

4

IGBT

41

diode

42

A driving

43

ignition input

44

current sensor

45

sensor input

8th

magnet system

91

Charging voltage uLade = uC - uL ₂

92

Magnetizing current iL ₁

93

Current iL ₂

94

Diode voltage uD

Claims (21)

Method for magnetizing a magnet system (8), wherein
the magnet system (8) is associated with a Magnetisierspule (22) and
the magnetizing coil is subjected to a current pulse having a limited pulse duration, whereby a magnetic field (B) interacting with the magnet system (8) is built up,
characterized in that the pulse duration of the current pulse is limited to a value between 10 μs and 500 μs and preferably between 10 μs and 200 μs. The method of claim 1, wherein
at least two magnetizing coils (22) are assigned to the magnet system (8),
the at least two magnetizing coils (22) are mutually arranged in such a way that their magnetic fields (B) are superimposed in reinforcing manner, and
the magnetic fields (B) of the at least two magnetizing coils (22) are constructed simultaneously. Method according to one of the preceding claims, wherein the current pulse by discharging one with the Magnetizing coil (22) electrically connected Capacitor element (21) is generated and the Magnetizing coil (22) and the capacitor element (21) be chosen and arranged one another such that the pulse duration of the current pulse to a value between 10 μs and 500 μs and preferably between 10 μs and 200 μs is limited. The method of claim 3, wherein the current pulse across a arranged parallel to the magnetizing coil (22) Return path (24) inductively into the capacitor element (21) is traced back, leaving an exponential leak the current in the Magnetisierspule (22) prevents and electrical energy is recovered. Application of the method according to one of the preceding Claims for magnetizing permanent magnets (8) Rare earth materials, such as those on the rotor an electric motor. Device (1) for magnetizing a magnet system (8), comprising
a pulse generator circuit (2) with
a capacitor element (21),
a magnetizing coil (22) electrically connected to the capacitor element (21) and
a switching element (23), by the actuation of which the magnetizing coil (22) can be acted upon by a current pulse with a limited pulse duration resulting from the discharge of the capacitor element (21) and thus the structure of a magnetic field (B) can be triggered,
characterized in that the pulse generator circuit (2) is constructed such that the pulse duration of the current pulse is limited to a value between 10 microseconds and 500 microseconds and preferably between 10 microseconds and 200 microseconds. Apparatus according to claim 6, wherein at least two Magnetizing (22) available and so mutually are arranged so that their magnetic fields (B) superimpose reinforcing, and at least one switching element (23) is arranged and operable such that the at least two magnetizing coils (22) simultaneously with each can be acted upon by a current pulse. Device (1) according to claim 7, wherein at least two Magnetizing coils (22.1-22.8) interleaved are. Device (1) according to claim 7 or 8, wherein each of the at least two magnetizing coils (22) a switching element (23) is associated and the device (1) further Actuating means (3), by means of which the at least two switching elements (23) simultaneously are operable. Device (1) according to any one of claims 6-9, wherein at least two capacitor elements (21) are present. Device (1) according to one of claims 6-10, wherein the pulse generator circuit (2) has a parallel to the magnetizing coil (22) arranged return path (24), which a storage throttle element (25) and in the direction of the discharge current pulse (iL ₁ ) blocking diode element (26). Device (1) according to claim 11, wherein the return path (24) is dimensioned such that it together with the Capacitor element (21) an electrical resonant circuit forms whose period longer, for example. 2- to 1000 times larger and preferably 10 to 100 times larger, is as the period of the pulse generator circuit (2) without the return path (24). Device (1) according to claim 12, wherein the storage throttle element (25) is a storage choke coil with an inductance (L _d ) which is 2 to 1000 times larger and preferably 10 to 100 times larger than the inductance (L ₁ ). the magnetizing coil (22). Device (1) according to one of claims 11-13, wherein the Pulse generator circuit several parallel to each other has switched storage throttle elements (25). Device (1) according to any one of claims 6-14, wherein the Device (1) at least two preferably identical Pulse generator circuits (2.1-2.4) has. Device (1) according to any one of claims 6-15, wherein the Capacitor element (21) a solid, flat, with a Includes metal layer provided dielectric, and preferably a foil capacitor. Device (1) according to any one of claims 6-16, wherein the Switching element (23) comprises a bipolar transistor (4) insulated gate whose collector (C) with the Magnetizing coil (22) is electrically connected. Device (1) according to claim 17, wherein the gate (G) of the bipolar transistor (4) with an insulated gate is controllable by a drive device (42) which has an ignition input (43) for an ignition pulse and a sensor input (45) for a signal of a the emitter current (I _E ) measuring current sensor (44), and the insulated gate bipolar transistor (4) from the drive device (42) is such that it locks when the current sensor (44) detects a negative emitter current (I _E ). Device (1) according to any one of claims 6-16, wherein the Switching element (23) includes a thyristor. Device (1) according to any one of claims 6-19, wherein in at least one magnetizing coil (22) already magnetized permanent magnet, preferably a NdFeB magnet, is inserted such that its magnetic field that magnetic field built up by the magnetizing coil (22) (B) reinforcing superimposed. Use of the device (1) according to one of the claims 6-20 for magnetizing permanent magnets (8) Rare earth materials, such as those on the rotor an electric motor.

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